1. Field of the Invention
This invention relates to wound-covering materials and a method for preparing the same. More particularly, it is concerned with wound-covering materials which are applied to a site of skin defect when the skin is defectively injured by a wound, a burn or the like, These wound-covering materials keep said site of the skin defect in a wet state, reduce pain and prevent microbial infection to facilitate regeneration of the epidermis.
2. Description of the Prior Art
The use of a dry dressing and wet dressing as a method and material for treating wounds including traumatic dermal wounds and wounds caused by removal of skin for dermatoplasty as well as wound associated with disease is known in the art. In the former, healing is achieved by maintaining the wounded site dry until a crust is formed. The latter is directed to creation of adequately wet circumstances to enable floating of the epidermal cells. It is recognized in the latter method that more rapid healing of the wound is accomplished, less dry necrosis is formed and a protective effect on the wound surface is produced.
It is pointed out, however, as to the use of a surgical drape, one of the wet dressing techniques, that there is retention of a large amount of exudate which is possibly reabsorbed through the wound surface, risk of infection is high and direct contact of the adhesive with the wound surface may be detrimental to healing of the wound. The drape is also apt to be separated from the wound surface. A drape having small projections attached to the surface to be in contact with the wound surface is available, however, it is difficult to remove.
In order to overcome these problems there have recently been made available covering materials using a biopolymer such as collagen, chitin or fibrin on the area that can be in contact with the wounded site or those in which a moisture-retaining ingredient is dispersed in the rubber base material in order to achieve close contact, non-adhesion and maintenance of a highly aqueous state. In addition, wound-covering materials previously proposed by us are available which comprise a biocompatible hydrogel-forming support layer (for example, of carboxymethyl-cellulose, alginate, hyaluronate or poly(meth)acrylate) in which at least a portion of the area to be in contact with the wounded site is coated with a water-repellent substance and a moisture permeation-adjusting layer which is formed on the side opposite to the area of said support layer to be in contact with the wounded site (Japanese Patent Application Laid-Open-to-Public No. 183760/1987). All of the above-cited materials have achieved their purpose to some extent.
Although the prior art wound covering materials as mentioned above are effective to some extent, there is a problem of physical property in use as a wound-covering material in that the material used in forming a biocompatible base layer in an area to be in contact with the wounded site is apt to undergo degradation or detachment. Furthermore, the materials from the degradation or the detachment may be recognized as a foreign matter with the risk of delaying healing of the wound. Further, although the moisture permeation-adjusting layer formed on the opposite side of the area of the support layer to be in contact with the wound is required to possess an adequate moisture-permeating capacity and a capacity of inhibiting microbial attack, a considerably limited scope of materials meet both of the requirements.
An object of the invention is therefore to provide wound-covering materials in which the presence of a highly aqueous layer assures the adequate retention of the exudate and good contact with but no adhesion to the wound surface and which the highly aqueous support layer in use is not easily decomposed or detached when contacted with the wound thereby facilitating healing of the wound, especially the regeneration of the epidermis to result in rapid therapy of the wound and, furthermore, in which the properties of the moisture permeation-controlling layer can be set considerably freely and a method for preparing the same.